Photographic silver halide emulsion stabilized with ethylene-diurea

ABSTRACT

A STABILIZED SILVER HALIDE PHOTOGRAPHIC EMULSION WHICH IS SENSITIZED WITH ALKYLENE OXIDE POLYMERS AND STABILIZED WITH ETHYLENE-DIUREA.

United States Patent @fice Patented June 1., 1971 3,582,346PHOTOGRAPI-IIC SILVER HALIDE EMULSION STABILIZED WITH ETHYLENE-DIUREAFritz Dersch, Binghamton, N.Y., assignor to GAF Corporation, New York,NY.

No Drawing. Filed July 18, 1968, Ser. No. 747,034

Int. Cl. G03c 1/34 US. Cl. 96-109 7 Claims ABSTRACT OF THE DISCLOSURE Astabilized silver halide photographic emulsion which is sensitized withalkylene oxide polymers and stabllized with ethylene-diurea.

The instant invention is directed to photographic emulsions and inparticular, to light-sensitive silver halide emulsions which aresensitized with alkylene oxide polymers and which contain therein as astabilizing agent ethylenediurea.

In the past the sensitivity of photographic emulsions, i.e.light-sensitive gelatino silver halide emulsions, has been increased bythe incorporation therein of various alkylene oxide polymers. Thesensitizing additives employed have been compounds such aspolyoxyalkylene ethers of hexatans or hexides which have at least onehydroxyl group replaced by a polyoxyalkylene radical, and which havealso contained at least one lipophilic radical such as a long chainaliphatic hydrocarbon radical or a long chain aliphatic monocarboxylicester. Compounds of this type have been incorporated into the emulsion,both prior to coating or subsequent thereto.

Furthermore, the sensitizing agents have been incorporated in asubstratum coating or in an over coating Which is placed in intimatecontact with the emulsion layer.

In addition to the above sensitizing agents, polyalkylene glycols and inparticular, higher poly glycols which have a molecular weight in excessof 400 have also been incorporated as sensitizing or speed enhancingagents. The useful poly glycols have been those which are the reactionproducts of compounds such as ethylene oxide, propylene oxide, butyleneoxide, ethylene glycol, diethylene glycol, etc.

It is noted, however, that while the aforementioned alkylene oxidepolymers increase the speed of the silver halide photographic emulsioncompositions containing said alkylene oxide polymers have an increasedtendency to become fogged as compared with photographic emulsions whichare not so sensitized. This fogging tendency is particularly pronouncedwhen photographic film coated with an alkylene oxide polymer. Theethylene-diurea may above described alkylene oxide polymers is subjectedto conditions such as prolonged development and storage at excessivetemperatures and humidities.

Therefore, the incorporation of the speed enhancing agents necessitatesthe employment of rather large quantities of anti-foggants in order toovercome the great susceptibility to fogging of the sensitizedphotographic emulsion. While the use of the anti-foggant is advantageousto overcome the fogging difiiculties, said anti-foggants offset theadvantage of the use of the sensitizing agent in that said anti-foggantsdecrease the speed of the resulting silver halide emulsion. That is tosay that when one uses an alkylene oxide polymer to increase the speedof the emulsion and then is forced to use an anti-foggant to eliminatethe disadvantages of the speed sensitizer, said anti-foggant decreasingthe speed of the silver halide emulsion with the resulting relativelysmall net increase in sensitivity of such a photographic emulsion.

Therefore, it is an object of the instant invention to provide asensitized silver halide photographic emulsion which has increased speedand/or contrast.

Another object of the instant invention is to provide a silver halidephotographic emulsion which is sensitized with an alkylene oxide polymerand stabilized so as to eliminate the fogging eifect of said polymer.

Yet, another object of the instant invention is to provide a stabilizedsilver halide photographic emulsion which is sensitized with an alkyleneoxide polymer and stabilized with ethylene-diurea.

It has unexpectedly been found that when one employs in combination withan alkylene oxide sensitizing agent in a photographic emulsionethylene-diurea having the structure that the resulting emulsion doesnot possess the unfavorable eifect of increased fogging. Furthermore,the combination of an alkylene oxide polymer and ethylene-diurea whileit increases the sensitivity of the emulsion also iniiproves thecontrast and covering power of the developed s1 ver.

Another advantage of the instant silver halide photographic emulsionsystem is the reduction of fog in high temperature processing aspracticed in modern, automatic or semi-automatic processing machines. Inthese cases an appreciable speed increase is obtained even with theadditional benefit of a fog reduction. The increased speed and reducedfogging tendencies are obtained by adding ethylene-diurea to aphotographic emulsion which is sensitized with an alkylene oxidepolymer. The ethylene diurea may be incorporated at any convenient timeduring the preparation of the silver halide emulsion. Thus, saidethylenediurea may be incorporated prior to coating or subsequentthereto. That is to say the silver halide emulsion which is sensitizedwith an alkylene oxide polymer may have added thereto theethylene-diurea during the formation thereof. It is preferred, however,to added the ethylenediurea shortly before coating. The ethylene-diureawhich is employed in connection with the instant invention may beprepared by the reaction of ethylene diamine and nitrourea in an aqueoussolution as discussed by Davis et al., {219123251 of the AmericanChemical Society, 51, 1797 The useful alkylene oxide polymers are allwell known chemical substances. They may, for example, be the reactionproduct of an alkylene oxide such as ethylene oxide, propylene oxide orbutylene oxide, etc., with a polyhydric alcohol such as ethylene glycol,diethylene glycol, nonaethylene glycol, decaethylene glycol,dodecaethylene glycol, ring dehydration products of hexitol, erythritol,1,4-butyne diol, etc. In particular, the useful alkylene oxide polymersmay be prepared by the methods disclosed in the Chemistry of SyntheticResins, pages 990994, published by Reinhold Publishing Corporation(1935).

The resulting product of the above reaction to form alkylene oxidepolymers are poly glycols. The useful poly glycols should in generalhave a molecular weight in excess of 300 and preferably of about 1500 orto 4000 or more. If desired, the useful poly glycols may be furthermodified by reaction with various mono or poly-functional etherificationor esterification agents to introduce lipophilic groups such asaliphatic hydrocarbon chains which may have from about 8 to about 18carbon atoms or more. Typical aliphatic hydrocarbon chains of this typewhich may be incorporated into the poly glycols include such hydrocarbonchains as n-octyl, n-dodecyl, n-tetradecyl, n-octadecyl, n-eicosyl, etc.Furthermore, other useful lipophilic groups include fatty acid halideswhich contain from about 8 to 20 carbon atoms such as n-octadecoyl,n-dodecoyl, n-tetradecoyl, n-oleyl, etc.

Therefore, useful alkylene oxide polymers which may be employed inconnection with the instant invention include, but are not limited to,are as follows:

Polyethylene oxide HO CH CH (CH CH O n CH CH OH Di-(polyethylene-glycoxy -decane O (CH2CH20)u C 112 CH-zO ll 0 2 2O)n CH2 CH20 H Polyethylene oxide oleyl ether HOCH CH O (CH CH O),,CH CH OC HPolyethylene oxide lauryl ether HOCH CH O(CH CH O) CH CH OC H wherein nis an integer greater than about 10.

As noted above, it has unexpectedly been found that when an alkyleneoxide polymer and ethylene-diurea are combined in a silver halidephotographic emulsion one obtains increased speed, covering power, andstability to fogging. The results obtained by this composition are notobtained by the use of either of the ingredients, i.e., an alkyleneoxide polymer or ethylene-diurea, alone, and it is speculated that thecombined effect of these two components is a synergistic one.

While the exact mode of operation of the instant invention is presentlyunknown, it is currently theorized that when ethylene-diurea and analkylene oxide polymer are combined in a silver halide photographicemulsion they react in a synergistic manner to increase the speed,covering power and stability to fogging thereof. This is offered merelyas a theory to explain the mode of operation of the instant inventionand should not be construed in any way as imposing a limitation thereon.

In general, the ethylene-diurea may be employed in the instantcomposition in amounts from about 0.5 to about grams per mol of silverhalide in the emulsion. The preferred amount of ethylene-diurea whichmay be employed is about 2 grams per mol of silver halide emulsion. Thesilver halide emulsion of the instant invention may be prepared in anyconventional manner, such as by emulsification and digestion or ripeningof the silver halide, the elimination of aqueous salts by washing, and asecond digestion or after-ripening to obtain increased sensitivity.

One standard procedure for preparing photographic silver halideemulsions is as follows.

1) Precipitation, wherein the silver halide is precipitated by theinteraction of a water-soluble silver salt and a water-soluble halide,in the presence of a carrier, e.g. gelatin.

(2) Digestion, wherein the above precipitate is heated for a period oftime at a raised temperature, e.g. 50 to 60 C., with or without theaddition of further carrier, e.g. gelatin.

(3) Washing, wherein the digested, solidified or set (e.g. by chilling)emulsion is washed to remove soluble salts.

(4) Melting out and second digestion, wherein the washed emulsion andthe resulting flowable emulsion is heated for a period of time, with orwithout the addition of further carrier, e.g. gelatin.

Of course, variations of the above four steps can be employed. Anemulsion, when used Without employing a step, such as (3), we call anunwashed, emulsion. An emulsion when used following completion of allfour steps, we call a washed, finished emulsion. The latter is the typeof emulsion generally used.

During the last step of the above process, i.e. the second or finaldigestion, the emulsion increases in sensitivity. Various substanceshave been employed in the past to increase the speed of the photographicemulsion. These substances may be added during one of the digestingsteps in the above process. Frequently, sulfur compounds such as theso-called sulfur sensitizers have been employed in connection with thistype of emulsion. For example, compounds such as allyl isothiocyanate,thiourea, thiocarbanilide, etc., have been added. These and other usefuladditives are described in U.S. Patents 1,574,944; 1,623,499; and2,410,689. In addition, the emulsion may be treated with salts of noblemetals, such as ruthenium, rhodium, palladium, iridium and platinum.Furthermore, the emulsion may be chemically sensitized with gold saltsas described in U.S. Patent 2,399,083 or stabilized with gold salts suchas water-insoluble gold compounds which are added during one of theabove-noted digestion steps in the preparation of the silver halidephotographic emulsion. Generally, these gold stabilizing compounds havea solubility as low as 0.03 milligrams per milliliters of water.

Useful compounds of this type are disclosed in U.S. Patents 2,597,856and 2,597,915 and include compounds such as potassium chloroaurite,potassium anrothiocyan-ate, ammonium aurothiosulfate, potassiumchloraurate and auric trichloride. In addition, the emulsion may bechemically sensitized with reducing agents. Polyamine compounds such asdiethylene triamine, triethylene tetramine, tetraethylene pentamine ortetrapropylene pentamine may be employed for this purpose. In addition,the reducing agents such as stannous salts, iminoaminomethane sulfinicacid, hydrazine, hydroxylamine, formaldehyde sulfoxylate or sodiumhydrosulfite may be employed as disclosed in U.S. Patents 2,487,850;1,623,499 and Belgium Patent 547,323 and French Patent 1,146,955.

In connection with the instant invention, one may employ gelatin as thecarrier in the silver halide emulsion in combination with otherlight-sensitive materials. In addition, one may use such carriers aspolyvinyl alcohol, polyvinyl pyrrolidone, casein, carboxy methylcellulose, hydroxyethyl cellulose, gums and other synthetic resins.

The present invention will now be described by reference to thefollowing specific examples. Such examples are presented for purposes ofillustration only, and the present invention is in no way to be deemedas limited thereto.

EXAMPLE I A silver halide emulsion in gelatin containing 2 mol percentsilver iodide and 98 mol percent silver bromide was prepared byemulsifying and digesting the silver halide and subsequently eliminatingthe aqueous salts therefrom by washing. The emulsion was then digestedagain and brought up to its maximum light-sensitivity. Conventionaladditives including stabilizers, hardeners and surfactants were thenadded to the emulsion. A 10% solution of polyethylene oxide lauryl ether(BRII 35, Atlas Powder Company, Wilmington, Del.) in water was preparedand added to the emulsion. In addition, a 10% aqueous solution ofethylene-diurea was also added to the emulsion. Samples of the emulsioncontaining about 0.6 mols of silver halide resulted. The emulsionsamples were coated on a cellulose ester base and dried. The samples ofthese film coatings were then exposed in a type 1B Sensitometer anddeveloped in a developer of the following composition:

Water-500 cc.

Sodium sulfite, anhydrous72.0 g. Hydroquinone8.8 g.

Sodium carbonate, monohydrated-56.0 g. Potassium bromide-4.0 g.

Water to make 10. 1.

As may be noted from the following table, the silver halide emulsion ofthe instant invention had increased covering power. The covering poweris obtained by dividing the optical density at maximum density by thegrams of silver 5 per square decimeter in the developed image layer.This improved covering power was accomplished without lowering themelting point of the emulsion.

TABLE 1 Quantity of Covering Quantity of ethylenepower, BRIJ 35 diureaRelative Durex. added (g.) added (g.) speed Fog l2 g. Ag/dm.

EXAMPLE II A silver halide emulsion in gelatin containing 2 mol percentsilver iodide and 98 mol percent silver bromide which was prepared as inExample I was coated on a film base. Subsequent to the coating, asolution containing 20 grams of gelatin in 1 liter of water, 1 gram ofpolyethylene oxide lauryl ether and 2 grams of ethylene-diurea wascoated thereon as an anti-abrasion layer.

The results obtained when the film base was exposed to a Type 1BSensitometer and developed in a developer having a composition as inExample I were identical with the results as obtained in Example I.

EXAMPLE III A silver halide emulsion in gelatin containing 2 mol percentsilver iodide and 98 mol percent silver bromide Was prepared and coatedon a film base as in Example II, with the exception that the coatingapplied as an antiabrasion layer did not contain ethylene-diurea. Theresults obtained after exposure and processing as described in Example Iwere similar to that obtained in Example I when no ethylene-diurea wasadded.

EXAMPLE IV A silver halide emulsion in gelatin containing 2 mol percentsilver iodide and 98 mol percent silver bromide was prepared as inExample I. The emulsion samples were coated on a suitable polyester baseand dried. Samples of film coatings were then exposed and developed in ahigh temperature rapid processing M-6 X-Omat system with the followingresults:

TABLE 2 Quantity of Covering Quantity of ethylenepower, B RH 35 diureaRelative max. added (g.) added (g.) speed Fog 12 g. Ag/dm.

As may be readily seen by the above data, the covering power of thecomposition of the instant invention was greatly improved over that of acomposition which did not contain an alkylene oxide polymer andethylene-diurea.

EXAMPLE VI A silver halide emulsion in gelatin containing 2 mol percentsilver iodide and 98 mol percent silver bromide was prepared as inExample I. A 10% solution of polyethylene oxide oleyl ether was employedinstead of the polyethylene oxide lauryl ether with the same results asobtained in Example I.

EXAMPLE VII A silver halide emulsion in gelatin containing 2 mol percentsilver iodide and 98 mol percent silver bromide was prepared as inExample I. A 10% solution of polyethylene oxide was employed instead ofthe polyethylene oxide lauryl ether with the same results as obtained inExample I.

EXAMPLE VIII A silver halide emulsion in gelatin containing 2 molpercent silver iodide and 98 mol percent silver bromide was prepared asin Example I. A 10% solution of di- (polyethylene glycoxy)decane wasemployed instead of polyethylene oxide lauryl ether with the sameresults as obtained in Example I.

Although we have referred throughout the present specification to theuse of silver halide emulsions, and in particular silver iodide andsilver bromide emulsions, it is to be understood that we intend toinclude, silver chloride, silver bromide and silver iodide either aloneor in combination as the light-sensitive salt to which other sensitizingmaterials have been added. It is also to be understoodthat othermodifications may be made in our process or materials without theparting from the invention, and they are intended to be taken limitedonly by the scope of the appended claims.

Suitable supports which can be employed in connection with the instantinvention include such conventional support materials as cellulose estersupports including the hydrophobic variety or the type having a surfacemade hydrophilic by partial saponification metals such as aluminum orzinc, terephthalic acid ester polymers, paper, glass, film and the like.

I claim:

1. A stabilized photographic emulsion composition having a speed asgreat as or not appreciably reduced from that of the unstabilized butsensitized emulsion compris- (a) a colloidal carrier;

(b) a light-sensitive silver halide;

(c) an alkylene oxide polymer in an amount effective to sensitize thephotographic emulsion; and

(d) ethylene-diurea of the formula:

in an amount efiective to stabilize the photographic emulsion.

2. The composition as defined in claim 1 wherein the alkylene oxidepolymer is polyethylene oxide lauryl ether.

3. The composition as defined in claim 1 wherein the colloidal carrieris gelatin.

4. The composition of claim 1 wherein said ethylenediurea is present inan amount of from about 0.5 to about 5 grams per mol of silver halide.

5. A process for stabilizing a sensitized photographic emulsion withoutappreciably reducing the speed of the emulsion from that of theunstabilized sensitized emulsion which comprises adding to aphotographic emulsion comprising a colloidal carrier, a light-sensitivesilver halide and an alkylene oxide polymer in an amount effective tosensitize the photographic emulsion, ethylene diurea of the formula:

NH CO-NH-CH CH NHCONH in an amount effective to stabilize thephotographic emul- 6. The process of claim 5 wherein the alkylene oxidepolymer is polyethylene oxide lauryl ether.

7. The process of claim 5 wherein said ethylene-diurea is present in anamount of from about 0.5 to about 5 grams per mol of silver halide.

References Cited UNITED STATES PATENTS 2,756,147 7/1956 Reynolds et al.96-109X 3,201,244 8/1965 Larson 96--109X NORMAN G. TORCHIN, PrimaryExamner R. E. FIGHTER, Assistant Examiner

